A local contractor recently closed up shop and we had a decent relationship with them and so attended the auction where they sold off their company assets and wound up purchasing a 31D and an ex military 21B. Both are straight machines and the mechanic, who were also hoping to have recruited, says they’re good solid runners with low hours and good maintenance histories while they’ve been with them. This said, can anyone share some experiences they’ve had with the two machine models? Things to check watch buy and maintain stock on for example. The 21 has a stiff neck, no cushion rides which I thought was strange for a mid 80’s machine. Look forwards to reading your replies. Thanks, 631G
Regarding the lack of cushion hitch on the 21, that probably simplified and removed cost. Also may have been stiffening to drop them from airplanes. I don't know about 621's, but I do know the 290M tractors saw parachutes.
Those military 621Bs are bullet proof after about 500 hours of working out the issues of old hoses. Most don’t have many hours and were started monthly when they were in Army/Reserve/NG units. RedDot makes an AC unit for it but you will have to create an adapter plate for it and weld it to the top. Transmission failures have been our biggest problem; but plenty of people can rebuild them for you. Cat wants crazy money for a new seat, there are electric air seats available instead of the hydraulic unit. Good luck to you.
Contractor, how do I get a better seat? I bought 8 of these and fixed them up to look original. Less than 100 hours..
Wilson Finley has aftermarket seats available but a quick google search for aftermarket equipment seats should yield good results too. The Komatsu dealer here in the SE also sells them
toughseats.com They're not at OEM quality level, but not priced at OEM level. I got the parts to repair the KAB 515 in our Terex TS14G from them.
We are using the tough seat too; high model 5052 in 24V. They work fine if they are used properly. Make sure you take the data plates off your old seats and put them on the new seats.